Background art for the present invention will be described taking a small-sized excavator depicted in FIG. 6 as an example.
The excavator includes a crawler-type lower travelling body 1, an upper slewing body 2 mounted on the lower travelling body 1 so as to be able to be slewed around an axis X perpendicular to the ground, and a working attachment AT attached to a front portion of the upper slewing body 2. The working attachment AT includes: a boom 3; an arm 4; a bucket 5; and respective hydraulic actuators which actuate the boom 3, the arm 4, the bucket 5, namely, a boom cylinder 6, an arm cylinder 7, and a bucket cylinder 8.
The upper slewing body 2 includes an upper frame 9, on which a seat stand 10, an operator's seat 11 provided on the seat stand 10, a canopy 12 which covers the operator's seat 11 at the upper side thereof, various operation devices, an engine and equipment related to the engine. There is another specification including, instead of the canopy 12, a cabin in which the seat stand 10 and the operator's seat 11 are installed, namely, a cabin specification.
As shown in FIG. 7, the upper frame 9 includes a bottom plate 13 and a floor plate 14 disposed above the bottom plate 13 at a vertical interval. Between the bottom plate 13 and the floor plate 14 is defined an underfloor space S1, in which a control valve unit and the like are installed.
“Front and rear” and “right and left” used herein refer to directions as viewed from an operator seated in the operator's seat 11.
The seat stand 10 is installed on the upper frame 9 at a position rearward of the floor plate 14, defining an under-seat space S2 under the operator's seat 11, between the seat stand 10 and the bottom plate 13 of the upper frame 9.
The upper slewing body 2 further includes a partition wall 15 and a separation wall 17. The partition wall 15 is vertically provided in an upper portion of the under-seat space S2 to define a front space 16, a front part of the under-seat space S2, above the floor plate 14. In the under-seat space S2, the space except the front space 16 constitutes an engine room.
The separation wall 17 is vertically provided to partition a lower portion of the under-seat space S2 and the underfloor space S1 forward thereof.
The excavator further includes an electric-component box 19 and a box stand 20 which are accommodated in the front space 16. The electric-component box 19 accommodates a lot of electric components 18 including a relay. For simplification of drawing, only one electric component 18 is depicted in FIG. 7 and FIG. 9, and only three electric components 18 are depicted in FIG. 8. The electric-component box 19 is vertically and detachably installed, while placed on the box stand 20, by bolting or the like.
The electric-component box 19 is a rectangular parallelepiped-like box, having a box-opening 19a opened forward. The seat stand 10 has a front wall 10a formed with a front opening 21 overlapping the box-opening 19a. The openings 21 and 19a allows work such as attachment and wiring of the electric components 18 to be performed at a front side of the seat stand 10 through the openings 21 and 19a. 
The partition wall 15 has a rear opening 22 which brings respective spaces forward and rearward of the partition wall 15 into communication with each other. The rear opening 22 allows maintenance work to be performed on a part of devices 23 located rearward of the front space 16 in the under-seat space S2, for example, an alternator and a stator motor, through the rear opening 22.
The excavator further includes a front cover 24 which closes the front opening 21 at a front side thereof and a rear cover 25 which closes the rear opening 22 at a front side thereof. The covers 24 and 25 are detachably attached to the seat stand 10 and the partition wall 15, respectively, with not-graphically-shown bolts or the like. FIG. 8 shows a state where the front cover 24 has been detached.
The excavator further includes a harness 26. The harness 26 is a wire bundle for interconnecting the electric components 18 in the electric-component box 19 and external devices outside the electric-component box 19, for example, a relay and a controller that controls the relay. The harness 26 includes: a first portion extending from the outside of the seat stand 10 to an upper right portion of the front space 16 through a wiring port 27 formed in a right sidewall 10b of the seat stand 10 or the like; a second portion located over the electric-component box 19 in the front space 16 and extending horizontally from the first portion to a laterally intermediate portion of the electric-component box 19; and a third portion extending vertically downward from the second portion in a frontal area in the electric-component box 19 to be connected to the electric components 18. In the front space 16, the harness 26 is fixed to the electric-component box 19 in an appropriate region with a clip 28. The harness 26 is, thus, routed in the approximately shortest path downward from the wiring port 27.
There is disclosed a technique for installing the electric components in the under-seat space in Japanese Patent Application Laid-open No. 2000-96609, Japanese Patent Application Laid-open No. 2002-242225, and Japanese Patent Application Laid-open No. 2003-13469.
Rearward of the front space 16 in the under-seat space S2, disposed is a maintenance-requirement device 23 which requires its maintenance. Maintenance work for the maintenance-requirement device 23 is performed at the front side of the seat stand 10 in a state where the front and rear openings 21, 22 are opened by respective detachments of the front and rear covers 24 and 25. Meanwhile, the electric-component box 19 closing the rear opening 22 obstructs the detachment of the rear cover 25 and the maintenance work; hence the electric-component box 19 has to be removed, at the minimum, to a position which allows a space and operator's vision for the work to be secured, desirably, to a position outside the front space 16. However, the harness 26, being routed in the approximately shortest path from the wiring port 27 to the electric components 18 with little allowance, prevents the electric-component box 19 from being removed along with the harness 26. The harness 26, therefore, has to be temporarily disconnected from the electric components 18 during maintenance work for the maintenance-requirement device 23 in order to allow the electric-component box 19 to be removed. This significantly degrades the efficiency in the maintenance work including subsequent restoration.
Besides, the harness 26, routed to the electric components 18 in the vertically shortest path, can allow water having infiltrated into the front space 16 due to damage to a sealing member or degradation thereof, for example, rainwater and cleaning water, to run down along the harness 26 to reach the electric components 18, thereby generating a possibility of malfunctioning or failure of the electric components 18.